Sulkin was on Disney Channel's Pass the Plate as Gregg from the UK. He had a recurring guest role on the Disney Channel series Wizards of Waverly Place, where he played Alex's love interest Mason Greybeck he reprised his role in 4 episodes of season 3 and returned to the series in its fourth season,[8] and through to its finale.[9]

In 2010 he went to New Zealand making a Disney Channel film Avalon High, which premiered on 12 November 2010.[11][12] In an interview with Kyle Martino, aired on Soccer Talk Live on the Fox Soccer Channel in the US, Gregg announced that he was a fan of Arsenal.

He reprised his role as Mason Greyback in The Wizards Return : Alex vs. Alex on Friday, 15 March on Disney Channel.

In 2012, Gregg was starred in the American teen drama series Pretty Little Liars as a recurring character, Wesley Fitzgerald brother of Ezra Fitz.

In February 2013, it was announced that Sulkin would play Julian Fineman in FOX's television adaptation of Lauren Oliver's young adult novel, Delirium. On 8 May, it was reported that Fox has decided not to pick up Delirium.[14]